It’s unusual to be able to date the vanishing of a species. The last time a dodo was seen, on the island of Mauritius, was probably in 1662, but no one knows how long the bird survived, unseen and in low numbers. The last confirmed sighting off a great auk took place on an island off Iceland, in 1844, but it’s likely that stray birds lived on for years, even decades. There have been no confirmed sightings of the ivory-billed woodpecker since 1969, but there are still those who maintain there are ivory-bills out there somewhere.
The extinction of the passenger pigeon is one of those unusual cases, and it happened a hundred years ago this Labor Day weekend. On September 1, 1914, Martha, a passenger pigeon who lived in an aviary at the Cincinnati Zoo, was found dead in her cage. At the time, Martha was believed to be the sole passenger pigeon left on Earth, and, in the intervening century, no evidence has emerged to contradict this. The passenger pigeon was once the most numerous bird in North America, perhaps in the world; it’s estimated that when the first European settlers arrived, at least one of every four birds on the continent was a passenger pigeon. The early colonists were awed by the vastness of the flocks, which contained hundreds of millions—perhaps billions—of birds. As late as the eighteen-seventies, passenger pigeons still could be seen passing overhead in astonishing, sky-darkening numbers; then, over the course of just four decades, the species, Ectopistes migratorius, dwindled down to Martha and her companion, a male named George. Then it was just Martha. And then there were none.
The passenger pigeon’s demise is usually represented as the result of remorseless slaughter, which it certainly was. But the bird’s story also contains an element of mystery, which in some ways is just as alarming.
Passenger pigeons roosted the way they migrated, in enormous flocks. This made them easy pickings for hunters, and the early English colonists wrote of killing hundreds at a go. Once the railroads were laid, the pigeons could be shipped to big-city markets, and the butchery reached a new level. In his book “A Feathered River Across the Sky” (reviewed in this magazine and in The New York Review of Books in January), the author Joel Greenberg describes one of the last great nesting colonies, which was sighted in northern Michigan, in 1878. Telegraph operators relayed the location of the flock to hunters and trappers hundreds of miles away, and soon so many descended on the area that “hotels and boardinghouses ran out of space.” Within a few days, more than a million birds were dispatched.
By the eighteen-nineties, the only passenger pigeon sightings were of small, ragged flocks. And this is what makes the bird’s extinction difficult to entirely explain. Once the passenger pigeon was no longer abundant, it also was no longer worth hunting, or at least no more worth hunting than any other medium-sized bird. So why didn’t it persist at low densities? In his recent book “Lost Animals: Extinction and the Photographic Record,” Errol Fuller, a British author, argues that an “additional factor” must have been at work in the species’ extinction, because “in a land as vast as the United States there can be no mopping-up hunting for a species as small as a pigeon.” (Fuller’s book contains a grainy and not particularly flattering photo of Martha standing in her cage in Cincinnati.)